May 18, 2022 5:14:13 am
Four months after it became the first Olive Ridley sea turtle to be satellite-tagged on the coast of Maharashtra, Prathama has returned to near its nesting beach — Velas in the Ratnagiri district —to the surprise of researchers. Prathama, which had left state waters sometime in late March, was spotted 80 km offshore near Velas beach.
Five Turtles — Prathama, Savani (on January 25), Vanashree, Rewa and Laxmi (on February 13 and 16) — were tagged with platform transmitter terminals (PTTs), which were fitted with epoxy resin on the carapace (hard shell) of the turtle in Ratnagiri district. Each transmitter weighs less than three per cent of the adult turtle’s body weight, which ranges between 40 and 45 kg. But on March 2, the researchers had lost contact with one of the turtles christened Laxmi.
Dr R Suresh Kumar, senior scientist from the Department of Endangered Species Management, WII, Dehradun, said had not anticipated the trajectory taken by Prathama. “My initial hypothesis was that these solitary nesting turtles will move into the deep sea to return now and then. However, all the tagged turtles have remained within the continental shelf.”
The continental shelf has relatively shallow water, which then gives way to the slope and then the deepsea ocean.
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The initial hypothesis by the researchers monitoring the turtles was that the turtles were likely to remain in the nearshore or shallow water, waiting for the ocean currents to begin their journeys into the deep sea further down to Lakshadweep or drift towards Oman or Somali coastline and return later this year in October-November to nearshore waters.
It was suspected that once the currents start to set in near the shore in March, the turtles will move into the deep sea. However, except Rewa, which is on the edge of the continental shelf, all are within the continental shelf. Kumar said he believes that Rewa is currently foraging. “I am assuming that the nutrient-rich food is brought up along the slope (continental shelf). I suspect that all these turtles will move to the place where Rewa is, where the food is available in good amount. Turtles are somehow able to predict ocean water circulation and they time themselves to be there where the food is going to come up.”
Kumar added, “The satellite tagging is helping us further understand their behaviour.”
Researchers from the Wildlife Institute of India (WII), Dehradun, and the Mangrove Foundation, an autonomous body under the Maharashtra government, are monitoring the turtles’ movement to understand the migratory pattern of the solitary nesting turtles.
Olive Ridley turtles are considered the most abundant sea turtles in the world with sporadic nesting in Maharashtra, Goa and the offshore Andaman Islands.
In Maharashtra, sporadic nesting is recorded across three districts in the southernmost region of the state — Raigad, Ratnagiri and Sindhudurg. In these three, the highest number of nests and hatchlings is recorded on the three beaches of Guhagar, Velas and Anjarle in the Ratnagiri district.
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